Nitrogen in Hydroponic Growing Medium of Tomato Affects the Demographic Parameters of Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae).

We evaluated the effects of different nitrogen levels (380, 310, 240, and 174 ppm) on the life history parameters of Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) on hydroponically cultured tomato plants. Our data show that there is a positive correlation between the nitrogen content and the demographic parameters, as the intrinsic rate of increase of T. vaporariorum was the lowest (0.059 ± 0.007 day(-1)) at 174 ppm and the highest (0.088 ± 0.005 day(-1)) at 380 ppm of nitrogen. The net reproduction rate (R 0), finite rate of increase (λ), and mean developmental time (T) were significantly influenced by the nitrogen levels. The mean longevity of males and females showed a positive relationship with the nitrogen level, ranging from 64.8 ± 3.96 to 76.3 ± 2.44 for males and 61.6 ± 5.35 to 71.2 ± 2.44 for females, observed in the lowest and highest nitrogen levels, respectively. The relationship between nitrogen fertilization and T. vaporariorum management on tomato crops is discussed.

Effects of glycine on the mouse neuromuscular junction.

Glycine was applied at a range of different concentrations to test possible effects at the neuromuscular junction of the mouse. The presynaptic control of acetylcholine (ACh) release and the postsynaptic activation of the nicotinic receptor have been analysed by means of extracellular recording with an EPC7 Patch Clamp amplifier. The results indicated that glycine did not modify in a significant manner the release of ACh and the postsynaptic cholinergic receptor function. Nevertheless, a significant increase in the rate of the conformational change of the receptor-ion channel complex seemed to be noteworthy. Glycine at 30 and 300 microM increased in a dose dependent manner the decay time of the spontaneous miniature current. Concentrations of glycine exceeding 10mM completely blocked the activity of the end-plate in this preparation. In conclusion, we proved that glycine does not affect most of the parameters of neurotransmission in the mouse but, it increases the conformational change of the postsynaptic complex, perhaps inhibiting the acetylcholinesterase activity.